This invention relates to electronic delay timers of the type employing a counter to establish the time delay period.
Delay timers of the electro-mechanical type are well known. Often they comprise a timer motor which drives a switch actuator to different switch contacts selectively positioned in the path of the actuator according to the amount of delayed time desired. Such timers generally have two modes: on-delay and off-delay. Briefly, in the on-delay mode, a normally open switch is closed at the end of the time delay to actuate, or turn on, the device to be controlled by the timer. In the off-delay mode, a normally closed switch is opened at the end of the delay to de-actuate, or turn off, the controlled device connected therewith.
Electronic timers are also known in which the delay time is established by the RC time constants of various, or variable, RC timing circuits. An example of such a timer is shown in the U.S. Pat. No. 3,859,543 of Milovancevic.
More recently, delay timers have become available which employ one or more counters that count pulses from an oscillator. Examples of such timers are shown in U.S. Pat. Nos. 3,714,519 of Swinea, Jr.; 3,950,657 of Sheng, et al.; 3,987,316 of Bogel, et al.; 4,035,661 of Carlson; and 4,021,646 of Meier.